Energy & Environment

New study reveals Burlington is trapping heat on par with much larger cities

Burlington ranks 13th out of 159 cities nationwide for risk factors that contribute to urban heat islands, according to a Climate Central study. Photo by Glenn Russell/VTDigger

A study published Wednesday revealed that Burlington is on average 7 degrees warmer, due to its design and layout, than rural areas of Vermont otherwise experiencing the same climate conditions. 

The Climate Central study ranked Burlington 13th out of 159 cities nationwide for risk factors that contribute to urban heat islands, with an index of 7.05 degrees Fahrenheit. Other cities with comparable scores include Baltimore, Miami and Chicago. 

“Burlington was probably the most surprising one hanging out at the top,” said Jen Brady, manager of analysis and production at Climate Central, the data scientist on the report.  

The main components considered for the score were greenery and permeable surfaces, which refer to how much of the ground is dirt, grass, or plants rather than asphalt or brick; building height; population density, which can sometimes contribute human-caused heat; and albedo, a measure of how much a city absorbs or reflects solar radiation.

Brady said Burlington scored well in greenery and permeable surfaces, since it boasts a lot of green spaces, such as parks and the Lake Champlain waterfront. Population density and building height also weren’t issues for Burlington. However, Burlington scored very low in albedo, which means it has unusually high heat absorption and does not reflect much solar radiation.  

The two other cities with albedo scores comparable to Burlington’s are Charleston, South Carolina, and New Orleans.

“We’ve noticed that often older, brick cities are absorbing more heat,” Brady said. She said cities in the Northeast consistently have lower albedo scores than cities in the Southwest. She cited Phoenix as an example, explaining that things like light-colored roofs and building materials affect albedo scores significantly. 

“We’re not saying Phoenix isn’t hot,” Brady said, “we’re just saying it isn’t much hotter than it has to be.”

That is not the case for Burlington.  

“I want people to understand the study isn’t necessarily about how warm your city is on the thermometer; it’s how much warmer is your city than it has to be because of the way that it’s built,” Brady said. 

As temperatures rise in northern states, the heat island score for Burlington may have an increasingly pronounced impact, and the city is yet to adopt a quantifiable urban heat island mitigation goal

“Urban heat islands kind of turn up the thermostat on top of an extreme heat event,” said Jeremy Hoffman, a national climate-change expert who is chief scientist at the Science Museum of Virginia. 

People living in urban heat islands generally experience higher-than-average rates of heat-related illnesses, especially outdoor workers and those with underlying respiratory issues, according to Hoffman. Both Hoffman and Brady emphasized that, if Vermont faces heat waves in the coming years, Burlington may need to take steps to ameliorate its exceptionally high heat island score so it can protect vulnerable residents. 

Things like green roofs — with flora grown on the roofs of existing buildings — or even painting buildings lighter colors can increase albedo scores significantly, reflecting more solar radiation away from the city. 

“In an older city like Boston or Burlington, you’re not gonna tear down buildings, but white roofs, or green roofs, reflective roofs, that can really make a difference,” Brady said. Additionally, creating shade structures and planting more trees can decrease heat island scores more generally.  

Hoffman said, as temperatures rise in coming years, Burlington officials will likely need outreach programs to keep vulnerable residents safe. He said subsidizing air conditioning in public spaces — such as libraries and community centers, so residents have somewhere to cool down during extreme heat waves — could minimize heat-related illnesses. 

While the Climate Central study did not map out heat distribution by neighborhood in Burlington, in 2020, the Urban Heat Island Severity dataset from the Trust for Public Land did. The dataset also examined areas surrounding Burlington including Winooski and South Burlington  

The map shows that areas with higher heat island intensity tend to be concentrated in northern parts of the city and Winooski. 

EPA’s environmental justice screening and mapping tool shows that northern Burlington’s population is more vulnerable to climate change impacts than residents in other parts of the city and surrounding areas, Hoffman said. That includes low-income people, those without a high school diploma, and people of color. The tool also shows that environmental factors such as air pollution and proximity to hazardous waste and to traffic are more of a problem in northern Burlington. 

Hoffman said a housing covenant enacted in the 1940s in South Burlington, which restricted people of color from buying homes there, likely played a role in vulnerable populations now facing more serious climate change risks in Burlington, just to the north.

“There’s a clear historical lens on present-day environmental inequity even in a city as small as Burlington,” Hoffman said. 

He emphasized that people living in neighborhoods with high urban heat island scores will suffer more. Brady echoed that sentiment, and said steps should be taken first at the local level. 

“Cities have to think, when I look around here, how could I make this cooler? When I go from neighborhood to neighborhood, what can I do to make this more comfortable and cooler based on the conditions around me?” Brady said.

Hoffman said people most vulnerable to climate change impacts should be part of the effort to come up with solutions.

“These populations have been left out of these conversations for generations, and if we leave them out of these conversations now, we aren’t any better than those decisions that were made a century ago,” he said.

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